Drainage control means for dishwashing apparatus and the like



March 4, 1958 J ANDREWS 2,825,350

DRAINAGE CONTROL MEANS FOR DISHWASHING APPARATUS AND THE LIKE Filed Nov. 1 l951 4 3 Sheets-Sheet 1 fizvewfaz" z/bfizz 15222 22205 2 March 4, 1958 J. L. ANDREWS 1 2,825,350

DRAINAGE CONTROL MEANS FOR DISHWASHING APPARATUS AND THE LIKE Filed Nov. 1, 1951 w 3 Sheets-Sheet. 2

i I I A March 4, 1958 J. L. ANDREWS ,8

DRAINAGE CONTROL MEANS FOR DISK-[WASHING APPARATUS AND THE LIKE Filed Nov. 1. 1951 I 3 Sheets-Sheet 3 65 meg-r mumm Z 1 a'eia'l'inv in! A gm" {I 1 v I I dfzzziwgzza'ewa United States PatentC DRAINAGE CGNTROL MEANS FOR DISHWASH- ING APPARATUS AND THE LIKE John L. Andrews, Oak Park, 111., assignor to General Electric Company, a corporation of New York Application November 1, 1951, Serial N 0. 254,288

1 Claim. (Cl. 134-186) This invention relates to an improved method of controlling the drainage of washing and rinsing liquid from dishwashers and like apparatus.

Broadly speaking, my invention is applicable to any apparatus in which quantities of liquid are periodically circulated within a vat and drained therefrom. Dishwashing apparatus is a typical example, for under control of a time-cycle switch, water for rinsing and washing the dishes is brought into and drained from the tub. A presently commercially successful domestic electric dishwasher includes a vat or tub within which are placed the dishes and utensils to be washed, means for automatically introducing into said vat a measured quantity of water, a motor driven impeller to circulate the water forcefully over and about the articles being washed, and valve controlled means for draining the water at the end of a washing or rinsing operation. Comparatively little water-usually only about twelve pints-is used for the respective washing and rinsing operations, and it has heretofore been considered essential to use drainage valves or equivalent mechanisms which positively close against loss of water during these operations. These valve devices are normally automatically controlled by a time-cycle switch or the like for operation at appropriate times during the operation of the apparatus; and although the valves are generally very reliable, they are potential sources of trouble in that their operating mechanisms may become deranged after long use or the valves themselves become clogged with particles of food waste and fail to close completely.

It is therefore a principal object of this invention to provide means whereby the drainage of liquid from a the washing and rinsing operations, and which provides for complete drainage or discharge of liquid when required by the operational cycle.

It is a further object of my invention to provide a dishwasher having an improved drainage system.

It is still another object of my invention to provide a dishwasher drainage system in which a clogged sewer or waste outlet will not result in leakage of water on to the floor of the building even though during such clogged condition liquid may be leaving the dishwasher under pump pressure.

Yet another object of my invention is to provide an improved impeller for a dishwasher.

It is still another object of my invention to provide a dishwasher having a free-draining vat and a rotatable impeller for circulating water throughout the vat, there being such relationship between the impeller and the adjacent wall of the vat that the rotation of the impeller prevents the water from leaving the vat.

During extensive studies of water flow and the pattern of recirculation in dishwashers of the impeller type it was r, 2,825,350 Patented Mar. 4, 1958 observed that as the water cascades from the dishes and walls of the washing vat and returns to the impeller for recirculation thereby, the rapidly rotating impeller blades scoop up a substantial depth of the water layer immediately about the impeller hub and throws it upwardly and away from the impeller. I then discovered that by a suitable relationship of the lower hub portion of the impeller to the bottom wall of the tub, desirably, although not necessarily, supplemented by the addition of structure about the base portion of the impeller hub to provide an outwardly directed pumping action, the lowermost layer of water may be kept from flowing beneath the impeller hub so long as the impeller was rotating; and by transferring the drainage port of the dishwasher from the usual location remote from the impeller to a position within the confines of the impeller hub it was found that the impeller itself could be made to operate as an efficient drainage control. No water reaches the drain port while the impeller-pump combination is in operation, and yet normal gravity drainage to the waste line, or alternatively, drainage to a sump supplying an impeller pump for discharging the water forcibly through a drainage system, occurs when impeller operation ceases.

In a presently preferred embodiment of my invention in which gravity drainage is contemplated, I provide a cluster of drainage openings at the bottom of the vat, said openings all being within the area of influence of the drainagecontrol means during operation thereof. Clearance is provided between said drainage control means and the bottom of the vat to permit food soil to pass to the drainage ports during the drainage operation. To reduce the possibility of scooping up food soil from the bottom of the vat and hurling it against the dishes being washed, the water circulation blades of the impeller are located at a higher level relative to the vat bottom. In a simple, effective, construction, the lower portion of the hub is provided with a plurality of angularly disposed slots which establish pumplike blades effective when the hub is rotating rapidly to drive the water outwardly along the bottom of the vat and thus prevent it from flowing beneath the hub and into the drain ports. When the impeller stops, however, the water may freely reach the drain ports for flow'to a plumbing waste line.

In dishwashers of the so termed preplumbed type, the spent washing and rinsing waters must be pumped from the dishwasher to a waste pipe inlet located substantially above the maximum free water level of the dishwasher vat, and in accordance with accepted plumbing code requirements means must be provided to insure that no polluted water will be syphoned or otherwise flow from the waste line into the dishwasher vat. Suitable protec tion against such an occurence may be had by providing a suitable vertical air gap between the overflow level or" the waste pipe inlet and the end of the discharge conduit of the dishwasher. It is common experience, however, that plumbing waste lines may become clogged; and in such a circumstance the discharge from the dishwasher would overflow through the air ports and fall to the floor. As a feature of my invention, I have provided a discharge fitting or guard valve which not only provides the necessary air gap to prevent pollution as above noted, but prevents spillage of water through the air ports. Novel means are provided to set up a recirculation from the dishwasher vat to the discharge fitting and then into the vat whenever the pump operates during a period in which the drainage fitting is closed to prevent such backsyphonage and spillage as above noted.

Gther features and advantages of my invention will be ently preferred embodiments thereof read in conjunction with the accompanying drawings, in which Fig. l is a side V a .7 if} meme if Y vention,-"c'ertain portions of the apparatus being 'in section 3 and other portions being broken away to reveal underly- Ting structure; Fig 2 is a plan section; taken through the da'ase" of the-impeller l nib on -lines oif-Eig. g1; fig; 3 "somewhat schematic elevation -ofithe impeller 'nd' ea-ting awat'er-eirculation:action w'v hi le the inipeller and i'ts .7 'sociat'ed drainage -cont'rol pump are irotatingg 'Fi'g, [4"iS' japla'n'cctionof the=d-1=ainage sump, taken fon'line's' 'k t wGfQFigLI-yEiQ. Sfis afront elevation of a dishwasher -of .ithe f pre plumbed type,'showingfa form of drainage sys- :t'e'm-aiid the anti -bac'kfiow: discharge fitting 'andjrecircula- 'ition-fm eans; Fig. -5 A'*is 'a structural detail: '-s'how ing 'a methodof securingthe sump to the dishwasherjfat; Pig. 6 is an enlarged vertical. section of the 'anti backflow device.

ra ndlrecirculationsystem: FigL;6A is fa somewhat schemat-V V iefiront elevation showing a'nianuer in which'dishwasher of Fig S-mayb eonneet a m' the'd'rainline of an" adjacent ekitchenjsink; and Fig. "7 isfa'plaii section taken through ample, waterrsprays from fit 11g 7 for'approximatel 45 "second'stlo fiushbfifobd'walstefrom the dishes; the I peller isquietjthr'oughoutfthis water inflow'periodi first rinse water is drained. Then, with the impeller ro- 5 tating, 'a measured quantity of water is admitted through iug period, means (not "shoe/i1) being providedfor'auto 1 V 'ture occurs. 'After'drainin'g wash waterywaterisam 'mitted fortw'o separate one-mihute rinses, during each ofswhich the impeller; is rotating so thatthe dishes ar'e subjected to "thorough fin sif actiqn iimder jmipeller' power. The rinsewateri'is drainedafter each rinse step.

The final rinse is followed by an extended drying-period 7 during which 'air warmed by the heating element 21 is a circulatedthroughout the vattby" the; airfan blades r'm impeller. "Afffthe" initial IS -I'seCb ejwatefi fitting 7 and the dishes are subjected to'a five-minute wash V matica lly adding detergent-to the. water during this'opera fi tion. Thiswash'watefisthendischargeditojthedfaiiijand' 10 a"second'washifig operation of similar duration and na 20 the quantities (twitter a guent washing and rip -.tl1'e=pump;chamber on lines 7+7 of Fig. 5.

' f-Reffll'fil'lg" now-to Fig.1 a dish'washing machine inc {1,367,341,Vdated FebruaIy 1.192;.

eludes an .outer casing; within whichis securely supported; a tuh'or'vat 3.1'The dishwasher is of the front ii 7 ;:opening "type; for example,-it may be similar t o that' sh own inxU. S; Patent- 2,422 Q22fissued June 10, 1917, .to; N.-. H. Koer'tge. ,Accordingly, the front wallportion (not shown) ofthe vatfhas a"large bpening which is Lfserveid bya bottom-hinged 'door. 'A's is well known, 7 h v V r fithe door maybe swung outwardl'y to asubstantiallyhori i zontaljposition; whereupon i'dish andhtensiI IeceiVifig gracksYtTnotfshown), slidablysupported Can-spaced Side frailsxsuch as the rail 5,. may'be'dr'awn out-of the 'v'at' on tdthedoonloaded with dishes andthe'like'to-be Washed;

-zandfreturned; to the Rat... Then after clo'singthe door, a timer-motor operated time-cycle switch 6 maybe 'op'erated-to conduct the dishwasher throu'gha series of automatic-oper'ations.including steps of rinsing, washing r ins ing, and :final drying; 7 cycles arerwellrknown; see. for example the 'typica-l'xform V 7 Shown in: Patent No; 2,536,256} entitled-Program 'Selec-. tor switch fl granted January 2, 19.5}, 'to -Ralph L. Berg, 1 @Udfls'signed to my' present 'assignee; 'The broad aspects o f'dishwashcr construction and control form no part of i'the present invention. 'It is. therefore beliet'ed suihcientj fgnerely 10 note that water is introduced into thevat a i through aninletjfitting 'fliservedby a solenoid er other .[electro-inotor' operated valves-assembly 8Whichjrec'eives water through' ouer'or more pipes 9 an'd' conducts it' through a' conduit 1910 'said inlet fitting. A motor 11 suitab ly"mounted below the v athas' 'itst shaft 12:.eXtending verticallywithin a 'guar'djube .14 for secureattacl V m'ent'to the-transverse wall of-th'e'thub 16 of an impeller 1 7 17, which is preferably substantially as shown in the Aabove noted" Koert'ge' Patentgl2,422",02 2.] The impeller lis thusjm ountedrfor rotation at motor :s'peed; impeller Y haslwater circulationblades '18" and-air circuiatio'n blades 20, the latter'enforcing airflow over and ahout {a ringlike hcatinglelement 21 of generally: circular shape and having terminalportigus (not' shqwny'for connection Qto'the electrical system ofithe apparatus. fltisi'underl stood ithat the apparatus will be connected throughits f control switch '6 to the'conventional ll=5fvolt alterfiating-.

" currentsys'tem oi the residence or other building in which The heating element fljis preferably of the sheathed conductor WPQQSShow-n and the dishwasher :is located described in the U. S.-"Pa tent to C. "A bbott 1:10.

Such controls and operational j x v location onlyeforpurposesi 'l l i Qtnir Alfl e a l 7 th waterinflowfs'uch 'me od's are u v Ferre because of: Variationsfin'waterfpfessure 1n;'c l1fierei1t '25firis'taliationsl rdifigly; it is preferredato "use :the f i fmte nnt a it hw in g;Auparams; I frentjdi'awnfby'theimpeller inotor'incr ou disclosed and; claimed as 'tlie of water; an-electromagneticall y operated is in'otor cireuit-{ope'i ates "to feSllflb liSh a 'circuit' t noidacft'uatedpwater valye which cl'ofs'es said valve.

It *hajsflfireiwidhslfhef'en noted th afconven'tib wearers hatiefeiiiployed mechanically or 'elec'tr'o spent washing oi' 'rin s'ing fliquid. The'gvalveles's cons umping; act-ion. associated with imp action to 131' en't lw'atei frdmmeaching' theraharay's drai n ports; i otheq-words, water c an eriter these 'pfdftsr any 'whe'n pellet is quietifollowi g'washin and; em mg eper a ioae firmer-m e this operati -constructfthej t 'dttem wan 22" of @the ivatf with! #gradu'aIslope toward the impeller hub, {and Tna terrace the outer wall areas of the-vat botto =re ctly to tIie impeHerI e f In the ig'ravity" drain an em :is suitably ecn r'ed'to 1 th 'bott relatioh t-he r'efwith. 7 am 11' grmay 'be attached a con iitidria foi' connec't-iofi td a braiiehi ofifthe p piping 27 serving the building fafsis well in" rsto' may,beimentioned lierethat e 7 tip 0 ran'gemeut."vvithin-itheidishwash" casiiig ould,

fbe'that' riiostaccessibleforinstallation tid flpal with theEhubjlimid guardjtube .f' i

it tprovidessa -su'itable plurality of drama 5. The guard tube 514 may advantageously b I I fof thesnmpstructnre; for examplefit mayf be 1; sc'r,ews1:or* equivalent 311;, The guardglt'ulie' laboverthemaxi'muriiffree e'r J v i :thusmahing: tieennecessawte like 'about'the-niotor sh hub 316 seabo entNoi. 199-531 8, grade ee seios'ea e nyecmated drain valves1toicontrolithei'discharge lot; h

fioi1 diseloged argd maimed hereini pp'enates 'the"b a'sist fside wallsbf theftub from flowingat as apid' ate di- V in'g' 'a bottom bell 's'ecufed i'n'wateftight relation'sto 7 bottom ofathe:surnpaby aagi'ornmet3fl offelastonieric ma .tterial-fclamped in positionbji a suitable numbe ormachine 34 does not extend appreciably beyond such a line. most important design aspect, of course, is for the lower beneath the hub to flow through the ports 28 into the sump and vents to the trap 26 and waste line 27. In practice, the clearance between the hub and wall 22, and the size of ports 28, provide for free passage of food soil particles such as small pieces of lettuce and other leafy vegetables, etc. 7

The drainage control means now to be described may, of course, be physically independent of the impeller, although it is economical and effective to form it as an element of the impeller itself. This has operational as well as structural advantages, for it will be noted that said control means operates together with the impeller, and a unitary construction makes it possible to employ a single driving connection between the impeller and motor.

As is conventional, the impeller 17 is preferably molded from thermo-setting plastic materials. In the Fig. 1 embodiment the drainage control structure occupies the lower edge portion of the impeller-that is, the wall surface below the entering edge of the blades 18-which is made substantially thicker than the remainder of the hub wall. As best shown in Fig. 2, this thickened wall portion is subdivided into a plurality of segments 32, each of which operates as a pump element. The spacing of adjacent elements affords passages through which water may reach the interior of the hub and the drainage openings 28. I have found that although the shape and relative angle of the end walls of the respective segments 32 are not critical, excellent results are obtained when the leading wall 33 of each segment inclines sharply rearwardly with respect to the direction of rotation of the impeller. The trailing wall 34 is sloped as desired to provide a wide entrance mouth for the passages defined by the leading and trailing walls of the adjacent segments. Its angle with respect to the direction of rotation does not appear seriously to influence the action of the impeller presently to be described. An eliective design results when the surface of each wall 33 is substantially tangential to the inner wall of the hub, and the walls 34 are so sloped that a diameter of the hub passing through the radially innermost end portions of the walls 33 will pass the radially outermost end portions of the walls 34 of the adjacent pump element. This arrangement gives strength and mass to the individual elements, provides a wide entrance mouth and a throat for each passage suficiently large to admit reasonably large food soil particles into the drainage area within the hub, and improves the action of the hub in the surrounding water. With the impeller driven in counterclockwise rotation by the motor 11, as indicated in Fig. 2, the attack angle of the leading walls 33 will throw water away from the hub in a generally rearward direction as respects the rotation of the hub. The trailing walls 34 cannot conflict with this action because no water can be thrown for wardly of a line normal to the surface of wall 33, and as above noted, the outermost edge of the trailing walls The sociated drainage-control pump is schematically shown in Fig. 3. Water draining from the dishes and side walls of the vat accumulates about the impeller hub to a depth which will submerge the leading or attack edges of the impeller blades 18. An upper layer of water will, therefore, immediately be thrown upwardly into the vat by the rapidly spinning impeller. That below the blades id will be repelled bythe pumping action of the surfaces 33. As this water stratum flows away from the hub along the gradually risingbottom wall 22 of the vat, it loses momentum because it is flowing countercurrent to the main water body. The eventual turbulence and intermixture terminates the stratification, and water which has been expelled by the surfaces 33 outwardly along the substantially flat bottom 22 of the tub will rise and be caught by the impellers 18 and thrown upwardly and outwardly thereby. The pumping surfaces 33 intercept water attempting to flow to the drainage ports, and therefore during washing and rinsing cycles in which the impeller is rotating very little water is lost. To drain the water from the vat between the several Washing and rinsing cycles above noted, it is necessary only for the impeller to stop for a sufiicient time to permit the water to drain into the sump, whence it flows to the drain trap and waste line. Accordingly, the time-cycle control 6 will provide for the necessary interruptions of the motor circuit.

The automatic dishwasher shown in partially sectional front elevation in Fig. 5 may be considered to be the same as that of Fig. 1 in all essential structural details and basic equipment. Instead of draining spent washing and rinsing liquid by gravity, however, the dishwasher is equipped with pumping means by which the liquid may be discharged to a waste line connected to the waste line of some adjacent fixture. For example, as shown in Fig. 6A, the dishwasher waste line may be connected to the trap of an adjacent kitchen sink. Dishwashers of this type are advantageous for installation in houses where the existing plumbing facilities do not readily lend themselves to direct connection to a standard waste trap such as the trap 26 of Fig. 1.

In this second embodiment, the impeller 46 has a relatively large diameter substantially cylindrical hub 41 from which extend conventional watercirculation blades 42 and air circulation blades 43. Instead of forming the impeller with a relatively thick lower hub portion as in Figs. 1 and 2, I have provided the hub with a ring 44 adhesively or otherwise secured to the inner wall of the hub and projecting slightly downwardly therefrom as clearly appears in Fig. 5. It will be understood that the portion of the ring below the hub will be formed with pumping sectors as in Fig. 2 and that the bottom wall 22 of the vat has drainage ports 23 as previously described.

A sump 45 is substantially deeper than the sump 24 of Fig. l; for reasons later appearing, the sump should accommodate the entire quantity of liquid used during any washing or rinsing operation. The sump may be removably attached to the bottom wall 22 of the vat by machine screws or equivalent .7 and an interposed gasket 48, as shown in Fig. 5A. As previously, a guard tube 59 extends from the bottom of the sump to a level well above the free water level in the washing vat to make it unnecessary to use stufiing boxes or the like about the motor shaft 51.

A plate 52 suitably secured within the sump 45 provides a lower pump chamber 53. An outlet 54 is preferably tangential to chamber 53 pursuant to conventional impeller pump construction. A suitable impeller pump may advantageously comprise a cast tubular hub 55 having an end wall 56 which may seat securely on a shoulder 57 provided on motor shaft 51. A convenient method of securing the hub for rotation by the shaft is by a drive key (not. shown) and nut 58. The impeller 40 may be securely fastened to shaft 51 by a nut 60 utilizing a lock Washer y ether conventional means to prevent the nut from loosening durin the (negation of the apparams' It will be noted that the guard tube, pllmgs'hub and peller hub are concentric and that the impeller hub'pasls through a suitable opening 61 in plate 52 providing an annular passage through which liquid draining from the vat may reach the pump chamber 53. The pump blades 62 may be integral with hub 55 as is conventional and may be of any suitable shape, see Fig. 7. As will later appear, the pump need not develop much head. The pump chamber discharge 54 connects by means of a conventional coupling nut 63 to a riser 64 secured to the outer wall of wat -3 b'y'a clamp 65 orfo'ther suitablexmeansq. Riser 64 terminates in a downwardly directed elb'owii66;

1 II have indicated at 67 a vertical iportion of'a wa-ste line jbranch which connectsto the drain line of an adjacent- ;kitchen sink (see Fig. 16A). Means are provided to prevent any possibility of sewage water from returning tothe dishwasher vat in the. event that the waste piping becomes fclogged to the extent'that water would back sup in' the 7 the dishwasher but,*partidularly with respectto valve 78,

' prevent; the liquid fromoverflowing throughthe air ports 7 "l6. It will be apparent thatif the liquid level rises suiii waste line portion 67;' and means are also provided to a f clamp '72s by means of whichthe body may be secured I Y 'toriser ti -iin concentricalignment with the mouth of it "elbow 66.- The upper end of body, 69 is belled for the telescopic reception of a cup 73.having a'transversely ex 7 V tendi' ngbottom wall 74'providedwith a central opening 7 5. V

' The side wall of cup 73 hasa suitable plurality. of relative lyla'rgearea air ports '76 which, as'i'sobvious, will "prevent any possibility of siphonage out of the branch waste line 67. To guard against the possibility of dish- 'wa'sher drainagei es'caping'through ports '76 as it flows "about the valve e'leme'nts within the'cup' 73, I employ a funnel-like structure 77 which projects below the level v of said air ports, as clearly' appears. a m a a For valve elements 'of, the .guard valve 68,;I'use a sphericalflotation -valve-78 and a 'disclike valve 80, the latter being slidably carried-on the'end of a stem 81 extending from a pole of the sphere 7 8. It-will benoted in Fig; 6 that stem 81 only partly enters the bore 82 in the body portion of valve'element stl'; said valve element is supported an a light coil spring 83 resting on spherefld.

' Valve elementSil has a slopingskirt portion d i which a under circumstances presehtly 'described', 'se'ats against thejlowermost edge of elbow 66, The normal position of {the respective 'valye elements is established by suitable V means such as a wire or. guard 86 supporting the sphere 73. i 'The oper'ation of the instant dishwasheris similar in all J respects to thatyof the previously described embodiment with one important'ditference: when washing or rinsing liquid is to'be discharged, th e impeller must be stopped foi an interval to permit drainage thiough ports zs into 7 the sump .45 and then restartedwhile the liquid is being a discharged from the sump. As previously noted, the

sump accommodates theentire quantity of'liquid used: in V 7 any one Washingor rinsing operation; When the motor a l t 1s restarted,liquid is pumped into riser 64 and ultimately jpass'es'downwardly over the .valve disc 86 through the.

; .f il'nnel opening and valve openings 75 into valve'b-ody 69 i nfly' t0 float. p e e, the rising sp er i car y'the valve disc sfl upwardly until the skirt portidnfiflithereof seats against the'bottom of elbow 66; V As'presentlyexplained,1this. becomes immediately refiective' :to throttle further discharge from said elbow even-if.- the pump remains in:operation and eventuallylseals theiend of the elbow'suificiently tovhaltiany furtherlflowi :However, at the initial stage of operation; under .cloggedi'draincondi 1 tions, water may. 'continue to enter/ he .valve'body .69, either from elbow 66 or by flowbackihroughbranchq'l and float 78 willfseat .against the rim of openingj to preventfany fiowlof liquid from branch 67 upwardly through the opening for "spillage over the air ports 76.

Spring 83 is sutficientlylight'to permit this t'lpwardmove- 'ment 'of 'sphere 78 to seated 'pros'ition, and as the spring compresses, iturges valve discsflmore firmly closed; To; 3 recapitulate, valve-disc seats as'the float' iti rises, and I it s eats befo're floati78 icomesinto seated position in the t 1 orifice'f/S; l l l V t Although the drain pump and may beincapable of pireventingfleakage into'cnp 73 under pump pressure conditions. theref ore 'provide H for recirculation of the water wheneverth pumpis opcrating-under clogged water line conditions. Specifically,

I install withinriser 64 a return {tube 90 .having' a'rverti- 'cally extending inlet end 91 which;;is preferably iconcentric within the riser; and adownwardly. sloping'pon' 'tion which passes through the wall "ofithe riser to terminate rat an 0pIllI1g 9. 2}Wlfl]i1:1jlhe \'at A guard-plate 93 is weldedcor otherwise? securedito the wall of the a 'vat to prevenLwatei-i discharge from 'tube, 90 over'1the dishes within the vat. The guard preferably has upper' and lower openings 94,although'itwillbe apparent that onlythe lower openings areessential;

. Da n n m "ope n-J4 is. v

' end is inconsistent withlthe ventryjjof thefwater 'into the "and'then through summi s air fitting as in the drain 9 5 line from the adjacent sink 87; The sink drain line has pletelvemptied into' the sump in a very short time, and

V conventional trap 83 connecting to: the waste piping (hot shown) of the building. -r'l he dishwasher vat may be corn- I it is onlyfneEessary' to provide a short interruption of operation. before the admission cf'new'liquid to the vat hinder control of theitime-cycle switch. The n l f' f s b :P ,F1 {jw'ate toprevent it I Sump- Therefore,

Q e new hquid 1s enterlng. If the plumb ng i c s c a I s V gbecarne clogged, 4t is'quite poss ble that l qu d will' remain in the branch-ei and any later discharge from the dishwasher could easily filLthe' guard 'valve bo'dyi692 edishwasher sump may be dis-- if it were not :for'the airports"76, pollutedwatercould siphon bacicintotherdishwaslier, for-asis clearly'evident in Fig. 6A, risero i forms the necessary long leg-of the. a

V rsiphcn'. The respective 'yalvesfigia-nd 'SG-notonly mezchanicallypreyent any haeltfiowefrorn:valve bodyf6$ into inythe appended claim; all tcnfmed' fie d ns' (within the true spirit andscope 19f tube. WhengvalveielementBQ seats, lion/ever,the kinetic energy ofwater.flow iis transformed 'substantially wholly l to static head pressure, withthe resultithatwaterireturns e to t-herdishwashervat throughtnbe '29. This operation may, of course, occur atany stage ofdishwasher action; cdnceivably, the, stoppagean'dfresul i g restl lrnfiow could. occur at the very outset of ;dishwasher1ope ration. "f'lhe. V 'time-cycle 'mechanism' 6 would nevertheless continneto. operate 'andatthe established, intervals; set; up the "elecl I trical circuits to. admit-water to, thelvat .and stojclosle the motor'circuit, However,.the measuring coil'of theabo noted'Merrill patent would. maintain tab trol of the water inlet va water is l is measuring coil,operates,to =closeage is blocked. 1

fAs earlier stated, the liquid pumping actionprovided' V by elements such as the sectors 32'appear1-to pmdtma more positive drainage control althoughlairelatiyely: smooth-iwaHed hub Lbelow the blades .al's orletfeetive. f V f Therefore, while there has; been. described ,whati is. at j pre'rsent considered, to bethe.;preferred embo'diments of the invention, it will lbe'under sto od that various modifica j tions maybe made therein,'.andz it ;is1 intended ention.

fis 'desig'nedly inca prablei of producing a much greater headtlianis necessary to, t carry the waste over theelbow 66, it must be remembered that the valve 80is at best-only; nelativelyflightlyv seated lie l he s t v valveelementsof.guard'valvei68"are;iin open positio'n water being pumped'u'pwardly thrqughi riser164 merely flows about the end91'of the tubefiqayithout entering it. 'Theaspirator' aetion oflwater flow aboutihe tube -n stile. It is therefore impossiblefltooverload" l the motor by excess water in the vat eventhou'gh drain l I claim:

In a dishwasher, a vat, means for introducing a quantity of liquid thereinto, an impeller in said vat for distributing said liquid thereabout, a sump below said vat and communicating therewith through at least one opening in the bottom of the vat, pumping means disposed within said vat to intercept liquid flowing to said opening and direct it away from said opening, pumping means in said sump, a motor common to said impeller and said two pumping means to operate the same, means for controlling the periods of operation of said motor, a discharge line from said sump rising to a downwardly extending outlet for discharge into a plumbing waste line or the like, valve means upstream of said point of discharge and arranged to close against backflow of liquid 10 from said waste line into said discharge line, and tubular means communicating between said discharge line and said vat to return pump discharge to said vat in the circumstance of operation of said motor while said valve means is in closed position.

References Cited in the file of this patent UNITED STATES PATENTS 1,927,943 Long Sept. 26, 1933 2,903,003 Marbury May 28, 1935 2,345,185 Edgar Mar. 28, 1944 2,422,022 Koertge June 10, 1947 2,492,288 Hollerith Dec. 27, 1949 2,545,490 Norris Mar. 20, 1951 

